1. Field Of The Invention
The present invention relates to an active matrix liquid crystal display (AMLCD) and, more particularly, to a method for manufacturing an AMLCD incorporating a thin film transistor (TFT) as a switching element and the structure by the same method.
2. Background Of The Invention
A conventional AMLCD is illustrated in plan view in FIG. 1. The conventional AMLCD includes a plurality of horizontally extending gate bus lines (or scan lines) 113 and a plurality of vertically extending source bus lines (or signal lines) 123. A pixel is enclosed by each gate bus line 113 and source bus line 123. The pixel includes a pixel electrode 125 coupled to the drain electrode 123b of a switching element, such as a TFT. Gate bus line protrusions serve as the gate electrodes of the TFTs while extensions from the source bus lines constitute the source electrodes 123a of the TFTs.
FIG. 2 illustrates a cross-sectional view of TFT of the conventional AMLCD taken along line 2--2 in FIG. 1. The TFT is provided on a transparent glass substrate 111 and includes a gate electrode 113a patterned along with gate bus lines 113 after a first metal layer of aluminum is deposited on the substrate.
During the patterning process, the first metal layer is etched after a photosensitive resin is deposited thereon and developed using a conventional photolithography technique. Namely, the photosensitive resin is coated over the entire metal layer and exposed using a photomask having opaque and transparent regions corresponding to the desired pattern. After exposure, the exposed portions of the photosensitive resin are removed to reveal portions of the underlying metal layer. These metal portions are then etched so that the gate bus lines 113 and gate electrodes 113a are formed in accordance with the mask pattern. The photosensitive resin is then removed.
A gate insulating layer 115 including SiN.sub.x is next vacuum deposited onto the substrate, followed by a continuous deposition of a-Si semiconductor layer 117 and n.sup.+ a-Si extrinsic semiconductor layer 119. These semiconductor layers are then etched in a second patterning process incorporating a similar photolithography technique as that described above. As a result, island portions are formed over each of the gate electrodes.
A second metal layer is next vacuum deposited onto the substrate, which is then etched in a third patterning process to form source bus lines 123, source electrodes 123a and drain electrodes 123b. During the third patterning process, a portion of the extrinsic n.sup.+ a-Si layer between the source and drain electrodes is also etched.
A second insulating layer 127 of SiN.sub.x is then vacuum deposited over the entire substrate surface to protect the TFT. A fourth patterning process is next carried out to form a contact hole over drain electrode 123b.
Lastly, a transparent conductive film, such as ITO (Indium Tin Oxide), is vacuum deposited over the entire substrate, and patterned in a fifth patterning process to form pixel electrode 125 making an electrical contact with the drain electrode 123b through the contact hole.
Thus, numerous patterning steps, each requiring a photolithography process, are performed in order to fabricate the conventional AMLCD. Each photolithography process involves depositing a photosensitive film or photoresist, providing a photomask with a desired pattern, exposing the photosensitive film to a light, and developing the exposed photosensitive film. As a result of such numerous patterning steps, production yield becomes low, and fabrication of the conventional AMLCD is complicated, lengthy and expensive.